<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Ajax</title>
</head>
<body>

    <div id="new"></div>

    <script>
        var message;
        if (!message) {
            alert("message is null");
        } else {
            alert(typeof message);
        }
        var num1 = 0.1;
        var num2 = 0.2;
        if (num1 + num2 == 0.3) {
            alert("sum is o.3");
        }
        if ("13" == 13) {
            alert(-64 >>> 5);
        }
       isNaN()
    </script>
</body>
</html>
